1. Field of the Invention
The present invention relates to a chemical injector for injecting a fluid chemical into a liquid or gas pipeline. In particular, the present invention is directed to a method and apparatus for a pipeline chemical injector which will promote atomization and dispersion of the injected fluid chemical in a manner superior to existing processes and devices.
2. Prior Art
Various industries utilize processes and devices wherein a liquid chemical is injected into a pipeline hauling a moving fluid stream. These industries include natural gas transmission and distribution, oil and gas production and gathering, petrochemical processing and refining, water conditioning and treating, and various types of chemical processing. By way of example, mercaptan may be injected into a natural gas pipeline as an odorant. Other examples of fluid chemicals injected into pipelines include corrosion inhibitors, paraffin inhibitors, and scale inhibitors.
Existing devices for injecting chemicals suffer from four basic drawbacks. The present invention seeks to address these concerns.
First, they are relatively complicated devices that require substantial modification to the pipeline with the concomitant expenditure for materials and labor. Once such devices are installed, they must remain in place. The optimum location for the injector depends on the chemical process. As the process changes, or as new process equipment is installed in or around the pipeline, the optimum location can change. Thus, it is beneficial for the injector to be easily removed and relocated.
A second drawback is pressure drop. The ability for a pipeline to carry fluid from one point to another is directly related to the addition of pumping pressure to the fluid. The energy cost of running a pump is the overhead cost of pipeline operation. Thus, any device within the pipeline that causes the loss of pressure results in a lowering of pipeline capacity and the subsequent loss in revenue. Thus, it is a great benefit for the chemical injector to minimize pressure loss. Many devices require substantial impingement of the area of the pipeline cross section. Such impingements result in pressure drop across the device and the resulting loss in flow capacity.
The third problem is fouling of the injector. In order to effectively atomize the injection fluid, a common means is by forcing the injected fluid through small ports in the injection tip. Experience shows that the viscosity of the injection fluid, along with long-term build-up of fine impurities in the injection fluid, results in the eventual fouling of the ports in the injection tip.
Fourthly, the use of small ports in the injection tip to effectuate atomizing requires the addition of pressurized equipment to force the injection chemical through the small ports and into the fluid flow. It is desirable to eliminate the need for additional capital expenditure for the pressurizing equipment.
Existing devices which seek to address these concerns are typically simple devices made up of a hollow tube which is open on one end. The opposed end of the hollow tube has a process connection that allows the device to be threadably received into a threaded coupling on the pipeline. Oftentimes there may be a check or isolation valve at the entrance to the injector device. These injectors introduce a jet of liquid chemical into a process flow without regard to the dynamics of atomization droplet formation by the laterally flowing fluid flow stream. Once a jet of liquid is injected directly into a fluid stream, the ability of that stream to atomize the liquid depends on the physical properties of the fluid stream moving through this pipeline. If the liquid is not atomized, it will collect as a liquid on the interior walls of the pipeline. Because the chemical injected is often a very reactable caustic or acidic fluid, liquid chemical directly impinging on the pipeline walls may cause corrosion.
Past approaches to chemical injection include McClintock (U.S. Pat. No. 3,734,111) which discloses introducing a second fluid into a pipeline with a first fluid by a sparger pipe 2 perpendicular to the pipeline having a series of holes 3 which are perpendicular to the flow of fluid in the pipe section. McClintock's device requires substantial pipeline modification, cannot be easily relocated and causes substantial pressure loss in the pipeline.
Sewell et al. (U.S. Pat. No. 4,995,915) discloses a chemical injector with an injector quill of any conventional design. The injection quill 11 is capable of injecting the liquid in such a way to mix the fluids in a finely atomized or mist form. The present invention is an ideal application for Sewell's requirements.
Dela (U.S. Pat. No. 5,277,250) discloses a chemical injector quill with a lower end of the quill stem closed by a removable plug or cap. Three staggered rows of jet openings 46 are uniformly spaced along its length in order to disperse chemical. Dela reveals that the invention is for liquid service. Furthermore, the numerous holes are subject to fouling and required pressurizing equipment. Also the requirement for the device to extend across the entire pipeline diameter causes pressure drop.
Ziemer (U.S. Pat. No. 6,165,372 and 6,238,557) disclose a first quill and a second quill with the second quill end spaced from the first quill end. Outlet tip ends 52 and 64 for the outlets of the quills are beveled and have notches 92 and 94, respectively, formed at the extremities in order to increase turbulence in the liquid stream. The notch or notches were not provided to encourage atomization and dispersion of the injected liquid into the gaseous stream. Tests of this configuration in a gaseous stream reveal that the injected liquid stream flows off the end of the injector tip without any atomization occurring.
There remains a need to improve two-fluid atomization methods and equipment.
There remains a need to provide an improved chemical injector to more efficiently atomize injected fluid chemicals into a pipeline stream without allowing the injected fluid to build up on the interior walls of the pipeline.
There remains a need to provide an improved chemical injector using the force of fluid flow through the pipeline to advantageously disperse injected fluid chemicals.
There remains a need to provide a chemical injector that effectively atomizes the injected fluid without clogging the injection apparatus.